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Automated Taxonomic Identification of Insects with Expert-Level Accuracy Using Effective Feature Transfer from Convolutional Networks
Stockholm University, Faculty of Science, Department of Zoology. Savantic AB, Sweden; Swedish Museum of Natural History, Sweden.
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Number of Authors: 52019 (English)In: Systematic Biology, ISSN 1063-5157, E-ISSN 1076-836X, Vol. 68, no 6, p. 876-895Article in journal (Refereed) Published
Abstract [en]

Rapid and reliable identification of insects is important in many contexts, from the detection of disease vectors and invasive species to the sorting of material from biodiversity inventories. Because of the shortage of adequate expertise, there has long been an interest in developing automated systems for this task. Previous attempts have been based on laborious and complex handcrafted extraction of image features, but in recent years it has been shown that sophisticated convolutional neural networks (CNNs) can learn to extract relevant features automatically, without human intervention. Unfortunately, reaching expert-level accuracy in CNN identifications requires substantial computational power and huge training data sets, which are often not available for taxonomic tasks. This can be addressed using feature transfer: a CNN that has been pretrained on a generic image classification task is exposed to the taxonomic images of interest, and information about its perception of those images is used in training a simpler, dedicated identification system. Here, we develop an effective method of CNN feature transfer, which achieves expert-level accuracy in taxonomic identification of insects with training sets of 100 images or less per category, depending on the nature of data set. Specifically, we extract rich representations of intermediate to high-level image features from the CNN architecture VGG16 pretrained on the ImageNet data set. This information is submitted to a linear support vector machine classifier, which is trained on the target problem. We tested the performance of our approach on two types of challenging taxonomic tasks: 1) identifying insects to higher groups when they are likely to belong to subgroups that have not been seen previously and 2) identifying visually similar species that are difficult to separate even for experts. For the first task, our approach reached 92% accuracy on one data set (884 face images of 11 families of Diptera, all specimens representing unique species), and 96% accuracy on another (2936 dorsal habitus images of 14 families of Coleoptera, over 90% of specimens belonging to unique species). For the second task, our approach outperformed a leading taxonomic expert on one data set (339 images of three species of the Coleoptera genus Oxythyrea; 97% accuracy), and both humans and traditional automated identification systems on another data set (3845 images of nine species of Plecoptera larvae; 98.6 % accuracy). Reanalyzing several biological image identification tasks studied in the recent literature, we show that our approach is broadly applicable and provides significant improvements over previous methods, whether based on dedicated CNNs, CNN feature transfer, or more traditional techniques. Thus, our method, which is easy to apply, can be highly successful in developing automated taxonomic identification systems even when training data sets are small and computational budgets limited. We conclude by briefly discussing some promising CNN-based research directions in morphological systematics opened up by the success of these techniques in providing accurate diagnostic tools.

Place, publisher, year, edition, pages
2019. Vol. 68, no 6, p. 876-895
National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:su:diva-177512DOI: 10.1093/sysbio/syz014ISI: 000498169600002PubMedID: 30825372OAI: oai:DiVA.org:su-177512DiVA, id: diva2:1384610
Available from: 2020-01-10 Created: 2020-01-10 Last updated: 2022-03-23Bibliographically approved
In thesis
1. Automated image-based taxon identification using deep learning and citizen-science contributions
Open this publication in new window or tab >>Automated image-based taxon identification using deep learning and citizen-science contributions
2021 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The sixth mass extinction is well under way, with biodiversity disappearing at unprecedented rates in terms of species richness and biomass. At the same time, given the currentpace, we would need the next two centuries to complete the inventory of life on Earthand this is only one of the necessary steps toward monitoring and conservation of species. Clearly, there is an urgent need to accelerate the inventory and the taxonomic researchrequired to identify and describe the remaining species, a critical bottleneck. Arguably, leveraging recent technological innovations is our best chance to speed up taxonomic research. Given that taxonomy has been and still is notably visual, and the recent break-throughs in computer vision and machine learning, it seems that the time is ripe to exploreto what extent we can accelerate morphology-based taxonomy using these advances inartificial intelligence. Unfortunately, these so-called deep learning systems often requiresubstantial computational resources, large volumes of labeled training data and sophisticated technical support, which are rarely available to taxonomists. This thesis is devoted to addressing these challenges. In paper I and paper II, we focus on developing an easy-to-use (’off-the-shelf’) solution to automated image-based taxon identification, which is at the same time reliable, inexpensive, and generally applicable. This enables taxonomists to build their own automated identification systems without prohibitive investments in imaging and computation. Our proposed solution utilizes a technique called feature transfer, in which a pretrained convolutional neural network (CNN) is used to obtain image representations (”deep features”) for a taxonomic task of interest. Then, these features are used to train a simpler system, such as a linear support vector machine classifier. In paper I we optimized parameters for feature transfer on a range of challenging taxonomic tasks, from the identification of insects to higher groups --- even when they are likely to belong to subgroups that have not been seen previously --- to the identification of visually similar species that are difficult to separate for human experts. In paper II, we applied the optimal approach from paper I to a new set of tasks, including a task unsolvable by humans - separating specimens by sex from images of body parts that were not previously known to show any sexual dimorphism. Papers I and II demonstrate that off-the-shelf solutions often provide impressive identification performance while at the same time requiring minimal technical skills. In paper III, we show that phylogenetic information describing evolutionary relationships among organisms can be used to improve the performance of AI systems for taxon identification. Systems trained with phylogenetic information do as well as or better than standard systems in terms of common identification performance metrics. At the same time, the errors they make are less wrong in a biological sense, and thus more acceptable to humans. Finally, in paper IV we describe our experience from running a large-scale citizen science project organized in summer 2018, the Swedish Ladybird Project, to collect images for training automated identification systems for ladybird beetles. The project engaged more than 15,000 school children, who contributed over 5,000 images and over 15,000 hours of effort. The project demonstrates the potential of targeted citizen science efforts in collecting the required image sets for training automated taxonomic identification systems for new groups of organisms, while providing many positive educational and societal side effects.

Place, publisher, year, edition, pages
Stockholm: Department of Zoology, Stockholm University, 2021. p. 66
National Category
Zoology
Research subject
Systematic Zoology
Identifiers
urn:nbn:se:su:diva-189460 (URN)978-91-7911-416-9 (ISBN)978-91-7911-417-6 (ISBN)
Public defence
2021-03-10, Vivi Täckholmsalen (Q-salen), NPQ-huset, Svante Arrhenius väg 20, Stockholm, 14:00 (English)
Opponent
Supervisors
Funder
EU, Horizon 2020, 642241
Available from: 2021-02-15 Created: 2021-01-25 Last updated: 2022-02-25Bibliographically approved

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